TECHNICAL SERVICE GUIDE

GE Consumer Products TECHNICAL SERVICE GUIDE Microwave Oven MODEL SERIES: JES2251SJ PUB # 31-9129

IMPORTANT SAFETY NOTICE The information in this service guide is intended for use by individuals possessing adequate backgrounds of electrical, electronic, and mechanical experience. Any attempt to repair a major ap pli ance may result in personal injury and property damage. The man u fac tur er or seller cannot be responsible for the in ter pre ta tion of this in for ma tion, nor can it assume any liability in connection with its use. WARNING To avoid personal injury, disconnect power before ser vic ing this prod uct. If electrical power is required for di ag no sis or test pur pos es, disconnect the power immediately after per form ing the nec es sary checks. RECONNECT ALL GROUNDING DEVICES If grounding wires, screws, straps, clips, nuts, or washers used to complete a path to ground are removed for service, they must be returned to their original position and properly fastened. GE Consumer Products Technical Service Guide Copyright 2004 All rights reserved. This service guide may not be reproduced in whole or in part in any form without written permission from the General Electric Com pa ny. 2

DANGER OF HIGH VOLTAGE AND HIGH TEMPERATURE (HOT/LIVE) OF THE INVERTER POWER SUPPLY (U) INVERTER WARNING This inverter board looks like a regular PCB. However, this PCB drives the magnetron tube with extremely high voltage and high current. NEW H.V. IT HAS: 1. Very high voltage and high current circuits. It functions the same as the high voltage transformer and high voltage capacitor in ordinary microwave ovens. 2. Aluminum heat sink that is energized with very high voltage and high heat energy. 3. Very high voltage which may remain in circuitry even when oven is off. High voltage charge may remain in the capacitors on the board. DO NOT: * 1. Do not touch circuitry because it has very hot (high voltage) circuitry. Even when replacing board, extreme care should be taken to avoid possible electric shock hazards. High voltage charge may remain in circuits. * 2. Do not touch aluminum heat sink because it is energized with very high voltage and is also very hot in high heat energy. * 3. Do not try to adjust or tamper with preset control on the inverter board because it is very dangerous to adjust without proper test equipment. * 4. Do not test oven while inverter grounding plate or screws are loose. It is very dangerous to operate H.V. inverter Circuit (U) with loose mounting screws or if improperly grounded. * 5. Do not try to repair inverter PCB because it is very dangerous to repair. Replace as a complete High Voltage inverter Circuit unit and return fully re-packed in original shipping box and shipping material. INVERTER POWER SUPPLY H.V. INVERTER(U) HEAT SINK DANGER OF HIGH VOLTAGE AND HIGH TEMPERATURE HOT/LIVE OF HEAT SINK IGBT CHOKE COIL RECTIFIER BRIDGE HIGH VOLTAGE TRANSFORMER CN702 (AC 120V) PRIMARY WINDINGS FILM CAPACITORS DO NOT ADJUST VR701 SECONDARY WINDINGS INVERTER BRACKET GROUNDING PLATE SAND BAR RESISTOR CN701 (PULSE 5V) SHORT FOR DISCHARGING HIGH VOLTAGE CHARGE REMAINS IN HIGH VOLTAGE CAPACITORS HIGH VOLTAGE CAPACITORS HIGH VOLTAGE CHARGE REMAINS IN HIGH VOLTAGE CAPACITORS HIGH VOLTAGE DIODES CN703 (HIGH VOLTAGE) DO NOT TOUCH 3

Specifications: Models: Specifications: Power Source: Power Requirement: Output: Microwave Frequency: Timer: Outside Dimensions: Oven Cavity Dimensions: Oven Cavity Size: Weight: PbF JES2251SJ 120V AC Single Phase, 60Hz 1500W 1200W 2450MHz 30 min. / Stage (HIGH Power) ~ 5 Stage Maximum 99 min. 99 sec. / Stage (Other Power Levels) ~ 5 Stage Maximum 7 8 9 16 23 (606mm)(W) x 19 (493mm)(D) x 14 (356mm)(H) 7 16 1 2 18 (469mm)(W) x 18 (470mm)(D) x 10 (278mm)(H) 2.2 cu.ft. 36 lbs. / 16.4 kg This product uses PbF Specifications subject to change without notice. 15 16 CONTENTS 1 FEATURE CHART... 5 2 CONTROL PANEL... 5 3 OPERATION AND DIGITAL PROGRAMMER CIRCUIT TEST PROCEDURE... 6 4 SCHEMATIC DIAGRAM... 8 5 DESCRIPTION OF OPERATING SEQUENCE... 9 6 CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING...11 7 DISASSEMBLY AND PARTS REPLACEMENT PROCEDURE... 13 8 COMPONENT TEST PROCEDURE... 17 9 MEASUREMENTS AND ADJUSTMENTS... 19 10 PROCEDURE FOR MEASURING MICROWAVE ENERGY LEAKAGE... 20 11 TROUBLESHOOTING GUIDE... 22 12 EXPLODED VIEW AND PARTS LIST... 25 4

1 FEATURE CHART FEATURE Five Stage Cooking Inverter Defrost Popcorn Sensor Cooking Sensor Reheat More/Less Timer Digital Clock Child Safety Look Add 1 Minute MODEL JES2251SJ O O O O O O O O O O 2 CONTROL PANEL Display Window Sensor Cooking Pads Popcorn Pad Inverter Defrost Pad Warm Pad Number Pads Power/Level Pad Add 1 Minute Pad Options Pad Clock Pad Timer Pad More/Less Pad Start Pad One tap allows oven to begin functioning. If door is opened or STOP/ RESET Pad is pressed once during oven operation, START Pad must again be pressed to restart oven. Stop/Reset Pad Before cooking: One tap clears your instructions. During cooking: One tap temporarily stops the cooking process. Another tap cancels all your instructions and time of day or colon appears on the display window. 5

3 OPERATION AND DIGITAL PROGRAMMER CIRCUIT TEST PROCEDURE 3.1. To set clock! OPERATION! SCROLL DISPLAY 1. Plug the power supply cord into wall outlet. 2. Press Clock pad. 3.3. Inverter defrost! OPERATION! SCROLL DISPLAY 1. Press Inverter Defrost Pad. INVERTER TURBO DEFROST 3. Enter time of day (TOD) by pressing appropriate! Number pads. 11 25 2. Set the weight for 1 lb by pressing Number pads. 1 Ib= 1 0 1.0! LB 4. Press Clock pad. TOD has now been resistered into the digital programmer circuit and will count up by minutes. 11 : 25 3. Press Start pad. 4. Press Stop/Reset Pad twice. Oven shuts off. 4 45! MIN SEC Time of day or colon if set appears in the display. 3.2. Time cooking for two stage! OPERATION! SCROLL DISPLAY 1. Place a water load in the oven. 2. Press Power Level pad once to set High power. (1st stage) 3. Set for 5 seconds by pressing Number pads. 5 Sec.= 5 P10 5 SEC 3.4. Popcorn! OPERATION! SCROLL DISPLAY 1. Press Popcorn pad once for 3.5 oz serving. (Select 3.5, 3.0, 1.75 oz) 3.5! OZ 2. Press Start pad. 3.5! OZ 4. Press Power Level pad 6 times to set Medium power. (2nd stage) 5. Set for 1 minute by pressing Number pads. 1 Min.= 1 0 0 6. Press Start pad. 7. When 1st stage cooking time has elapsed. Oven beeps twice and automatically switches to 2nd stage cooking. 8. When 2nd stage cooking time has elapsed, oven beeps 5 times and shuts off. P5 1 00! MIN SEC 5 SEC 1 00! MIN SEC Time of day or colon if set appears in the display 3. About 5 to 8 seconds later, cooking time will show on display. (Note) When cooking time has elapsed, Oven beeps 5 times and shuts off. 2 08! MIN SEC Time of day or colon if set appears in the display. Note: 5 to 8 seconds is the voltage detecting time, and the cooking time shown on display is determined by the detected voltage. 6

3.5. Warm! OPERATION! SCROLL DISPLAY 1. Press Warm pad. KEEP WARM 3.7 To set/reset child safety lock! OPERATION! SCROLL DISPLAY 1. Press Options pad. SELECT FUNCTION 2. Set for 1 minute by pressing Number Pad. 1 Min.= 1 0 0 1 00! MIN SEC 2. Press Number pad to select 5. 3. Press 1 to select child lock on. CHILD LOCK ON/OFF ON PRESS 1, OFF PRESS 2 CHILD LOCK ON 3. Press Start pad. 4. When cooking time has elapsed, Oven beeps 5 times and shuts off. 1 00! MIN SEC Time of day or colon if set appears in the display. 4. If you want to reset, please press Options pad. 5. Press Number pad to select 5. SELECT FUNCTION CHILD LOCK ON/OFF ON PRESS 1, OFF PRESS 2 3.6. Sensor cooking! OPERATION! SCROLL DISPLAY 1. Pour 150 ± 15cc (4.5 ± 1/2 ozs) of room temperature water in beaker in the center of the oven. Press Sensor Reheat pad twice. 2. Press Start pad. 3.The steam sensor detects steam about 1.5 to 4 minutes after the start pad is pressed. Sensor cooking (T1) automatically switches to cooking time(t2). "Sensor" disappears with beep sounds and the remainder of cooking time appears in the display window. 6. Press 2 to select child lock off. 3.8. Power level CHILD LOCK OFF!Press Power Level!! Power Level! Display Window! once! P10 (HIGH)! P10! twice! P9!! P9! 3 times! P8!! P8! 4 times! P7 (MED.HIGH)! P7! 5 times! P6 (MEDIUM)! P6! 6 times! P5!! P5! 7 times! P4!! P4! 8 times! P3 (MEDIUM-LOW)! P3! 9 times! P2!! P2! 10 times! P1 (LOW)! P1 Cooking time will vary depending on the water temperature, the shape of the beaker or the Power source Voltage. 4. When cooking time has elapsed, Oven beeps 5 times and shuts off. Time of day or colon if set appears in the display. 7

4 SCHEMATIC DIAGRAM (DC 4000V) YELLOW BROWN ORANGE BROWN/GREEN BLUE/BLUE (PULSE 5V) 8

5 DESCRIPTION OF OPERATING SEQUENCE 5.1. Variable power cooking control High Voltage Inverter Power Supply (U) controls output power by the signal from Digital Programmer Circuit (DPC). Power relay stays ON for P3 to P10 and For P1 to P2, both inverter drive signal and power relay to control output power. The ON/OFF time ratio does not correspond with the percentage of microwave power since approximately 2 seconds are required for heating of magnetron filament. Variable Power Cooking POWER SETTING OUTPUT POWER(%) APPROX. ON-OFF TIME OF POWER RELAY (RY1) ON(SEC) OFF(SEC) HIGH P10 100% 22 0 P9 90% 22 0 P8 80% 22 0 MEDIUM-HIGH P7 70% 22 0 MEDIUM P6 60% 22 0 P5 50% 22 0 P4 40% 22 0 MEDIUM-LOW P3 30% 22 0 P2 20% 15 7 P1 10% 8 14 DEFROST P3 30% 22 0 5.2. Inverter power supply circuit NEW H.V. The Inverter Power Supply circuit powered from the line voltage, 120V 60Hz AC input supplies 4,000V DC to the magnetron tube, and functions in place of the H.V. transformer, the H.V.capacitor and H.V. diode. 1. The AC input voltage 120V 60Hz is rectified to DC voltage immediately. 2. DC voltage will be supplied to the switching devices called IGBT. These devices are switched ON-OFF by the 20 to 40 khz PWM (pulse width modulation) signal from the microcomputer in the DPC. 3. This drives the High voltage transformer to increase voltage up to 2,000V AC. 4. Then the half-wave doubler voltage rectifier circuit, consisting of the H.V. diodes and capacitors, generates the necessary 4,000V DC needed for the magnetron. 5. Output power of the magnetron tube is always monitored by the signal output from the current transformer built into the inverter circuit. 6. This signal is fed back to the microcomputer in the DPC to determine operating conditions and output necessary to control PWM signal to the Inverter Power Supply for control of the output power. 5.3. Inverter defrost When the Auto Control feature is selected and the Start pad is tapped: 1. The digital programer circuit determines the power level and cooking time to complete cooking and indicates the operating state in the display window. Table shows the corresponding cooking times for respective serving by categories. Inverter Defrost SELECTED WEIGHT COOKING TIME 1.0 LB 4 min.45 sec. 2. When cooking time in the display window has elapsed, the oven turns off automatically by a control signal from the digital programmer circuit. 5.4. Sensor cooking Auto sensor cooking without setting a power level or selecting a time. All that is necessary is to select an Auto Sensor Program before starting to cook. Understanding Auto Sensor Cooking As the food cooks, a certain amount of steam is produced. If the food is covered, this steam builds up and eventually escapes from the container. In Auto Sensor Cooking, a carefully designed instrument, called the steam sensor element, senses this escape of steam. Then, based upon the Auto Sensor Program selected, the unit will automatically determine the correct power level and the proper length of time it will take to cook the food. Auto Sensor Cooking is successful with the foods and recipes found in the Auto Sensor Cooking Guide. Because of the vast differences in food composition, items not mentioned in the Cooking Guide should be prepared in the microwave oven using power select and time features. Please consult Variable Power Microwave Cookbook for procedures. 9

AUTO SENSOR COOKING/REHEAT PROCESS T2 = T1 X K = 2 min. and 40 sec. X 0.2 = 160sec. X 0.2 = 32 sec. P1 P2 K Factor Category Power Power Standard Oatmeal HIGH HIGH 0.2 Explanation of the Auto Sensor Cooking process 1. During the first 10 second period there is no microwave activity. When calculating the T2 time by using the formula below make sure this 10 seconds is subtracted from the T1 time. In other words, T1 time starts at the end of the 10 second period. 2. T1 time The total amount of time it takes the microwave oven to switch to T2 time after the 10 second period. 3. T2 time When the steam escapes from the cooking container placed in the oven, the steam sensor detects it and the microprocessor calculates the balance of cooking time. This T2 time is then shown in the display and begins counting down. Balance of cooking time (T2 time) The balance of cooking time which is called T2 time, can be calculated by the following formula. T2 time (in sec.) = T1 time X K factor Remember, the T1 time starts after the 10 second period. The coefficient K is programmed into the microprocessor memory and they are listed in the following tables along with the P1 and P2 powers. When "More" or "Less" pad is selected, the K factor varies resulting in T2 time to be increased or decreased. Example of calculating the T2 time Example 1: If the T1 time is measured to be 2 minutes and 40 seconds after the 10 second period, and the Auto program selected is Oatmeal: 5.5. Sensor reheat Auto Sensor Reheat is a quick and easy way to reheat refrigerated and room temperature foods. Simply press the reheat pad. There is no need to select power level and cooking time. The Auto Sensor Reheat process is same as Auto Sensor Cooking process. Category P1 P2 K Factor Power Power Standard Sensor Reheat HIGH MEDIUM 0.3 5.6. Steam sensor and digital programmer circuit In order to determine if the steam sensor function of the digital programmer circuit is working, do the following test. 1. Place a water load (150 cc) in the oven. 2. Tap Sensor Reheat pad. 3. Tap Start pad. 4. Steam Sensor detects steam about 1.5 to 4 minutes after the Start pad is tapped. 5. T1 time cooking automatically switches to remaining time for cooking (T2). 6. The remaining cooking time (T2) appears in display window. If the following cooking time appears, Steam Sensor function is normal. T1 TIME T2 TIME (Remaining cooking time) 1 Min. 30 Sec. ~ 4 Min. 18 Sec. ~ 48 Sec. 5.7. Thermistor The thermistor which fixed on magnetron detects magnetron temperature and make power down when the temperature becomes abnormal high. A normal thermistor's resistance values for temperature ranges between 75-85 degree F is from 37k to 57k 10

6 CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING Unlike many other appliances, the microwave oven is a high voltage, high current device. It is free from danger in ordinary use, though extreme care should be taken during repair. Caution Servicemen should remove their watches whenever working close to or replacing the magnetron. 6.1. Check the grounding Do not operate on a two wire extension cord. The microwave oven is designed to be grounded when used. It is imperative, therefore, to ensure the appliance is properly grounded before beginning repair work. 6.2. Inverter warnings DANGER, HIGH VOLTAGE AND HIGH TEMPERATURE (HOT/LIVE) OF THE INVERTER POWER SUPPLY (U) The High Voltage Inverter Power Supply handles very high voltage and current for the magnetron tube. Though it is free from danger in ordinary use, extreme care should be taken during repair. The aluminum heat sink is also energized with high voltage (HOT), do not touch when the AC input terminals are energized. The power device Collector is directly connected to the aluminum heat sink. The aluminum heat sink may be HOT due to heat energy, therefore, extreme care should be taken during servicing. H.V. Inverter warning WARNING FOR INVERTER POWER SUPPLY (U) GROUNDING Check the High Voltage Inverter Power Supply circuit grounding. The high voltage inverter power supply circuit board must have a proper chassis ground. The inverter grounding bracket must be connected to the chassis. If the inverter board is not grounded it will expose the user to very high voltages and cause extreme DANGER! Be sure that the inverter circuit is properly grounded via the inverter grounding bracket. GROUNDING PLATE H.V.INVERTER(U) CHECK GROUNDING HEAT SINK RECTIFIER BRIDGE HIGH VOLTAGE TRANSFORMER CN702 DO NOT ADJUST VR701 SAND BAR RESISTOR CN701 SHORT FOR DISCHARGING HIGH VOLTAGE CHARGE REMAINS IN HIGH VOLTAGE CAPACITORS DANGER OF HIGH VOLTAGE AND HIGH TEMPERATURE HOT/LIVE OF HEAT SINK HIGH VOLTAGE CAPACITORS HIGH VOLTAGE CHARGE REMAINS IN HIGH VOLTAGE CAPACITORS IGBT CHOKE COIL PRIMARY WINDINGS FILM CAPACITORS SECONDARY WINDINGS HIGH VOLTAGE DIODES CN703 DO NOT TOUCH Grounding of the inverter circuit board WARNING! DISCHARGE THE HIGH VOLATGE CAPACITORS For about 30 seconds after the oven is turned off, an electric charge remains in the high voltage capacitors in the Inverter Power Supply circuit board. When replacing or checking parts, remove the power plug from the outlet and short the inverter output terminal of the magnetron filament terminals to the chassis ground with an insulated handle screwdriver to discharge. Please be sure to touch the chassis ground side first and then short to the output terminals. 11

2. When replacing the fuse, confirm that it has the appropriate rating for these models. 3. When replacing faulty switches, be sure the mounting tabs are not bent, broken or deficient in their ability to hold the switches. 6.5. Avoid inserting nails, wire etc. through any holes in the unit during operation. Never insert a wire, nail or any other metal object through the lamp holes on the cavity or any holes or gaps, because such objects may work as an antenna and cause microwave leakage. MAGNETRON FILAMENT TERMINAL Discharging the high voltage capacitors WARNING There is high voltage present with high current capabilities in the circuits of the primary and secondary windings, choke coil and heat sink of the inverter. It is extremely dangerous to work on or near these circuits with the oven energized. DO NOT measure the voltage in the high voltage circuit including the filament voltage of the magnetron. WARNING Never touch any circuit wiring with your hand or with an insulated tool during operation. 6.3. Part replacement. INSULATED HANDLE SCREWDRIVER Touch chassis side first then short to the terminal of the magnetron filament terminal. When any part or component is to be replaced, always ensure that the power cord is removed from the wall outlet. 6.4. When the 18A fuse is blown due to the operation of the short switch: WARNING When the 18A 120V fuse is blown due to the operation of the interlock monitor switch, replace all of the components (primary latch switch, door switch, short switch and power relay B (RY1)). 1. This is mandatory. Refer to adjustments and measurements for the location of these switches. 6.6. Confirm after repair 1. After repair or replacement of parts, make sure that the screws of the oven, etc. are neither loose nor missing. Microwave might leak if screws are not properly tightened. 2. Make sure that all electrical connections are tight before inserting the plug into the wall outlet. 3. Check for microwave energy leakage. (Refer to procedure for measuring microwave energy leakage). CAUTION MICROWAVE RADIATION USE CAUTION NOT TO BECOME EXPOSED TO RADIATION FROM THE MICROWAVE MAGNETRON OR OTHER PARTS CONDUCTING MICROWAVE ENERGY IMPORTANT NOTICE The following components have potentials above 2000V while the appliance is operated. Magnetron High voltage transformer (Located on inverter (U)) High voltage diodes (Located on inverter (U)) High voltage capacitors (Located on inverter (U)) Pay special attention to these areas. When the appliance is operated with the door hinges or magnetron installed incorrectly, the microwave leakage can exceed more than 5mW/cm 2. After repair or exchange, it is very important to check if the magnetron and the door hinges are correctly installed. 6.7. Sharp edges Caution Please use caution when unpacking, installing or moving the unit, as some exposed edges may be sharp to the touch and cause injury if not handled with care. 12

7 DISASSEMBLY AND PARTS REPLACEMENT PROCEDURE 7.1. Magnetron 1. Discharge high voltage charge. 2. Remove 2 screws holding air guide A on the oven cavity. 3. Remove 1 screw holding air guide B. 4. Remove 1 screw holding themistor. 5. Remove 2 screws holding reinforce bracket. 6. Disconnect 2 high voltage lead wires from magnetron filament terminals. 7. Remove 4 screws holding the magnetron. After replacement of the magnetron, tighten mounting screws properly in an x pattern, making sure there is no gap between the waveguide and the magnetron to prevent microwave leakage. CAUTION When replacing the magnetron, be sure the antenna gasket is in place. 7.2. Digital programmer circuit (D.P.C) Before handing the D.P.C ensure that your body is connected to ground to discharge any electric charge. 1. Disconnect all connectors from D.P.C. 2. Remove 1 grounding screw. 3. Remove 1 screw holding escutcheon base and slide the escutcheon base upward slightly. 4. Remove 1 screw holding D.P.C. 5. Release lock of connector CN6 by pushing both levers to inside pull upward, and remove flat cable of membrane keyboard. 6. Separate D.P.C board from tabs on the escutcheon base and remove D.P.C board. 1. The membrane key board is attached to the escutcheon base with double faced adhesive tape. HOW TO DISCONNECT SPECIAL LOCK CONNECTOR 2 PULL 1 PRESS THIS LEVER LOCKING LEVER 13

7.3. Low voltage transformer and/or power relays (RY1, RY2) Be sure to ground any static electric charge built up on your body before handling the D.P.C. 1. Replace D.P.C. board. CN6 CN1 7.4. Fan motor ESCUTCHEON BASE CN3 CN2 CN4 LOW VOLTAGE TRANSFORMER RY1 RY2 1. Disconnect 2 lead wires from fan motor terminals. 2. Remove 2 screws at location on oven attaching orifice assembly. 3. Remove orifice assembly from oven assembly. 4. Remove fan blade from the fan motor shaft by pulling it straight out. 5. Remove 2 screws holding fan motor to orifice. 6. Separate the fan motor from the orifice assembly by freeing 2 catch hooks on the orifice assembly. 7.5. Door assembly 1. Remove door C from door E by carefully pulling outward, starting from upper right hand corner using a flat blade screwdriver. 2. Separate door E from tabs on door A and remove door A. 3. Open Door E at the opening angle of approximately 10 (Note: The door cannot be removed if the opening angle is greater than 10 ). 4. Remove the door E from its hinges by pushing the door E upward and out. 5. Remove door screen B from door A. 6. Remove door key and door key spring. To re-install components: 1. Place the door s lower hinge pin into the bottom hinge hole. 2. Use your left index finger to support the door s lower hinge pin while guiding the door s upper hinge pin into the top hinge hole. 3. Lower your finger to seat the door onto the hinges. 4. Replace other components. Door alignment is crucial. If door is misaligned, apply pressure until alignment is achieved. After replacement of the defective component parts of the door, reassemble, and perform microwave leakage test. DOOR A DOOR KEY DOOR A DOOR KEY DOOR KEY SPRING DOOR E DOOR C 14

7.6. Turntable motor 1. Remove the motor cover by cutting, at the locations indicated by the arrows, with a cutter. After removing the motor cover, be sure that cut portions are properly trimmed or bent to the inside so that no sharp edges will be exposed to outside. 2. Disconnect 2 lead wires connected to the turntable motor. 3. Remove the turntable motor by removing screw. After replacing the new turntable motor and reconnecting the two lead wires, reinstall the motor cover by rotating it 180, tucking the tabs into the base in the 2 provided slots, then screw the single tab to the base using a 4mm X 6mm screw. 7.7. Steam sensor 1. Disconnect connector CN2 from digital programmer circuit board. 2. Disengage catch hooks on sensor cover C from orifice. 3. Remove steam sensor from orifice. When installing the steam sensor, make sure that the direction of steam sensor is as shown in figure. SENSOR COVER B SENSOR COVER C HOOK ORIFICE BASE MOTOR COVER HOOK TURNTABLE MOTOR 15

7.8. Inverter power supply CAUTIONS 1.Always leave the grounding plate in place. 2.Always securely tighten the ground screw through the bottom of the chassis (base). 3.Securely connect 3 lead wire connectors. 4.Make sure the heat sink has enough space (gap) from the oven. Take special care not to dress any lead wire over the aluminum heat sink because it is hot. 1. Remove cabinet outer panel and discharge high voltage charge. 2. Remove the the H.V.lead wire from magnetron terminals. 3. Disconnect 2 connectors from CN701 & CN702 on H.V.Inverter(U). 4. Remove 1 screw holding grounding plate to the base. 6. Press 1 encircled locking tab and then slide 4 locking tabs of Inverter bracket at the bottom of the base in direction of arrows. 7. Remove 1 screw holding H.V.Inverter to Inverter bracket. 5. Bend back 2 locking metal tabs on the base. 8. Remove 1 screw holding grounding plate to H.V. Inverter. 16

8 COMPONENT TEST PROCEDURE CAUTIONS NEW. H.V. 1.High voltage is present at the high voltage terminal of the High Voltage Inverter (U) including aluminum heat sink during any cook cycle. 2.It is neither necessary nor advisable to attempt measurement of the high voltage. 3.Before touching any oven components, or wiring, always unplug the oven from its power source and discharge the high voltage capacitors. 8.1. Primary latch switch (door switch and power relay B) interlocks. 8.3. Magnetron Continuity checks can only indicate an open filament or a shorted magnetron. To diagnose for an open filament or shorted magnetron. 1. Isolate magnetron from the circuit by disconnecting the leads. 2. A continuity check across magnetron filament terminals should indicate one ohm or less. 3. A continuity check between each filament terminal and magnetron case should read open. 1. Unplug lead connectors to Power Relay B and verify open circuit of the power relay B 1-2 terminals. 2. Unplug lead connectors to Primary Latch Switch and Door Switch. 3. Test the continuity of switches at door opened and closed positions with ohm meter (low scale). Normal continuity readings should be as follows. Door Closed Door Opened Primary Latch switch 0 (Close) (Open) Door Switch 0 (Close) (Open) Power Relay B (Open) (Open) 8.2. Short switch & monitor 1. Unplug lead wires from Inverter Power Supply (U) primary terminals. 2. Connect test probes of ohm meter to the disconnected leads which were connected to Inverter Power Supply (U). 3. Test the continuity of short switch with door opened and closed positions using lowest scale of the ohm meter. Normal continuity readings should be as follows. 8.4. Membrane key board (Membrane switch assembly) Check continuity between switch terminals, by tapping an appropriate pad on the key board. The contacts assignment of the respective pads on the key board is as shown in digital programmer circuit. (Refer to Mini Manual) Door Opened 0 Door Closed 17

8.5. Inverter power supply (U) DO NOT try to repair H.V. Inverter Power Supply (U). Replace complete H.V. Inverter(U) Unit. a. After approximately 3 seconds, oven stops. b. During oven operation, input current is approximately 0.4A. HEAT SINK RECTIFIER BRIDGE DANGER OF HIGH VOLTAGE AND HIGH TEMPERATURE HOT/LIVE OF HEAT SINK IGBT CHOKE COIL!! INPUT AMPERE! FAILURE CODE! Unplug CN701! <0.4A! Oven stops in 3!!!! seconds after started. HIGH VOLTAGE TRANSFORMER CN702 DO NOT ADJUST VR701 PRIMARY WINDINGS FILM CAPACITORS SECONDARY WINDINGS If both a and b check OK, the Inverter Power Supply (U) can be determined to be OK. SAND BAR RESISTOR CN701 HIGH VOLTAGE DIODES CN703 SHORT FOR DISCHARGING HIGH VOLTAGE CHARGE REMAINS IN HIGH VOLTAGE CAPACITORS HIGH VOLTAGE CAPACITORS HIGH VOLTAGE CHARGE REMAINS IN HIGH VOLTAGE CAPACITORS DO NOT TOUCH DANGER HIGH VOLTAGE Test if failure codes of H97 or H98 appear by doing the following procedure. It is recommended to use an AC line input current Ampere meter for testing. Test1 1. Program DPC. a. Tap Clock keypad b. Tap Timer keypad c. Tap Start keypad d. Tap Power Level keypad 2. Place 1 liter of water load into oven cavity. 3. Unplug 2 pin H.V. lead wire connector CN703 from magnetron tube. 4. Program oven at High power for 1 minute and press start. a. After approximately 23 seconds, oven stops. b. During oven operation, input current is approximately 0.5 to 1A. If both a and b are OK, proceed to test 2.!! INPUT AMPERE! FAILURE CODE! Unplug CN703! 0.5 to 1A! Oven stops in 23!!!! seconds after started. Test2 Continued from Test 1 1. Unplug 3 pin connector CN701. CN703 remains unplugged. 2. Program oven at High power for 1 minute and press start. 18

9 MEASUREMENTS AND ADJUSTMENTS SWITCH GAP SHOULD BE <0.7MM. ACTUATOR LEVER WB27X10833 SCREW DOOR PRIMARY LATCH SWITCH 9.1. Adjustment of primary latch switch, door switch and short switch. 1. Mount the Primary latch switch, the door switch and the short switch to the door hook assembly as shown in ILL. No specific individual adjustments during installation of the Primary latch switch, door switch or short switch to the door hook are required. 2. When mounting the door hook assembly to the oven assembly, adjust the door hook assembly by moving it in the direction of the arrows in the illustration, so that the oven door will not have any play in it. Check for play in the door by pulling the door assembly. Make sure that the latch keys move smoothly after adjustment is completed. Completely tighten the screws holding the door hook assembly to the oven assembly. 3. Reconnect the short switch and check the continuity of the monitor circuit and all latch switches again by following the component test procedures on P.17. 4. Measure microwave energy leakage after servicing. DOOR HOOK ASSY SHORT SWITCH SECONDARY LATCH SWITCH SCREW 01-033 9.2. Measurement of microwave output The output power of the magnetron can be determined by performing IEC standard test procedures. However, due to the complexity of IEC test procedures, it is recommended to test the magnetron using the simple method outlined below. Necessary Equipment: *1 liter beaker *Glass thermometer *Wrist watch or stopwatch Check the line voltage under load. Low voltage will lower the magnetron output. Take the temperature readings and heating time as accurately as possible. 1. Fill the beaker with exactly one liter of tap water. Stir the water using the thermometer and record the water's temperature. (recorded as T1). 2. Place the beaker on the center of glass tray. Set the oven for High power and heat it for exactly two minutes. 3. Stir the water again and read the temperature of the water. (recorded as T2). 4. The normal temperature rise at High power level is as shown in table. TABLE (1L-2min.test) RATED OUTPUT 1200W TEMPERATURE RISE Min. 37 o F 19

10 PROCEDURE FOR MEASURING MICROWAVE ENERGY LEAKAGE WARNING Check for radiation leakage after every servicing. After repairing or replacing any radiation safety device, keep a written record for future reference, as required by D.H.H.S. and Health regulation. This requirement must be strictly observed. In addition, the leakage reading must be recorded on the service repair ticket while in the customer's home. The U.S. Government standard is 5 mw/cm 2 while in the customer s home. 2mW/cm 2 stated here is our own voluntary standard. 10.1. Equipment Microwave leak detector Glass thermometer 212 F or 100 C 600cc glass beaker 10.2. Procedure for measuring radiation leakage Note before measuring. Do not exceed meter full scale deflection. Leakage monitor should initially be set to the highest scale. To prevent false readings the test probe should be held by the grip portion of the handle only and moved along the shaded area in Figure no faster than 1 inch/sec (2.5cm/sec). Leakage with the outer panel removed... less than 5mW/cm 2. Leakage for a fully assembled oven with door normally closed... less than 2mW/cm 2. Leakage for a fully assembled oven [Before the latch switch (primary) is interrupted] while pulling the door... less than 2mW/cm 2. 1. Pour 275 ± 15cc (9ozs s ± 1/2oz) of 20 C ± 5 C (68 ± 9 F) water in a beaker which is graduated to 600cc, and place in the center of the oven. 2. Set the radiation monitor to 2450MHz and use it following the manufacturer s recommended test procedure to assure correct results. 3. When measuring the leakage, always use the 2 inch (5cm) spacer supplied with the probe. 4. Tap the start pad or set the timer and with the magnetron oscillating, measure the leakage by holding the probe perpendicular to the surface being measured. 10.2.1. Measurement with the outer panel removed. Whenever you replace the magnetron, measure for radiation leakage before the outer panel is installed and after all necessary components are replaced or adjusted. Special care should be taken in measuring around the magnetron. WARNING Avoid contacting any high voltage parts. 10.2.2. Measurements with a fully assembled oven. After all components, including outer panel are fully assembled, measure for radiation leakage around the door periphery, the door viewing window, the exhaust opening and air inlet openings. 10.3. Record keeping and notification after measurement After any adjustment or repair to a microwave oven, a leakage reading must be taken. Record this leakage reading on the repair ticket even if it is zero. A copy of this repair ticket and the microwave leakage reading should be kept by repair facility. 20

10.4. At least once a year, have the radiation monitor checked for calibration by its manufacturer. WARNING AVOID CONTACTING ANY HIGH VOLTAGE PARTS. 01-035 MOVE PROBE ALONG SHADED AREA( )AROUND EXHAUST OPENINGS AND AROUND AIR INLET OPENING 21

11 TROUBLESHOOTING GUIDE DANGER HIGH VOLTAGES 1. DO NOT RE-ADJUST PRESET CONTROL on the H.V.Inverter (U). It is very dangerous to repair or adjust without proper test equipment because this circuit handles very large current and high voltage. Operating a misaligned inverter circuit is dangerous. 2. Ensure proper grounding before checking for trouble. 3. Be careful of the high voltage circuitry, taking necessary precautions when troubleshooting. 4. Discharge high voltage remaining in the H.V.Inverter (U). 5. When checking the continuity of the switches or the H.V.Inverter, disconnect one lead wire from these parts and then check continuity with the AC plug removed. To do otherwise may result in a false reading or damage to your meter. When disconnecting a plastic connector from a terminal, you must hold the plastic connector instead of the lead wire and then disconnect it, otherwise lead wire may be damaged or the connector cannot be removed. 6. Do not touch any parts of the circuitry on the digital programmer circuit, since static electric discharge may damage this control panel. Always touch yourself to ground while working on this panel to discharge any static charge in your body. 7. 120V AC is present on the digital programmer circuit (Terminals of power relay s and primary circuit of Digital Programmer Circuit). When troubleshooting, be cautious of possible electrical shock hazard. Before troubleshooting, operate the microwave oven following the correct operating procedures in the instruction manual in order to find the exact cause of any trouble, since operator error may be mistaken for the oven s malfunction. 11.1. (Trouble) Oven stops operation during cooking SYMPTOM CAUSE CORRECTIONS 1. Oven stops in 3 seconds after No 120V AC is supplied to H.V.Inverter (U) CN702 1. Latch Switch pressing start pad terminals 2. Power relay RY-1 3. Loose lead wire connector CN701, CN702 Oven stops in 23 seconds after H.V.Inverter (U) operates by the control signals 1. Magnetron pressing start pad from DPC but magnetron is not oscillating 2. Loose lead wire connector CN703 Oven stops in 10 seconds after pressing start pad (Auto sensor cooking) 2. No display and no operation at all. Fuse is blown. Steam sensor circuit does not function Most probably loose connection of connectors,or door latch mechanism is not adjusted properly 1. Steam sensor 2. DPC 3. Loose wiring connector CN2 1. Allign door, Door Latch Switches 2. Loose wiring connectors AC INPUT 120V HIGH VOLTAGE TO MAGNETRON CONTROL SIGNAL IN/OUT APPROX 2-3V 22

SYMPTOM CAUSE CORRECTIONS 1. Oven is dead. 1. Open or loose lead wire harness Check fan motor if thermal cutout is defective. Fuse is OK. 2. Open thermal cutout No display and no operation at all. 3. Open low voltage transformer 4. Defective DPC 2. No display and no operation at all. Fuse is blown. 3. Oven does not accept key input(program) 4. Fan motor turns on when oven is plugged in with door closed. 5. Timer starts count down but no microwave oscillation. (No heat while oven lamp and fan motor turn on) 6. Oven can program but timer does not start countdown. 7. Microwave output is low. Oven takes longer time to cook food. 1. Shorted lead wire harness Check adjustment of primary, secondary latch 2. Defective primary latch switch (NOTE 1) switch and short switch including door. 3. Defective short switch (NOTE 1) 4. Defective Inverter Power Supply (U) NOTE 1: All of these switches must be replaced at the same time. Check continuity of power relay B (RY-1), s contacts (between 1 and 2) and if it has continuity, replace power relay B (RY-1) also. 1. 2. Key input is not in proper sequence Open or loose connection of membrane key pad to DPC (Flat cable) Refer to operation procedure. 3. Shorted or open membrane key board 4. Defective DPC Refer to DPC troubleshooting. 1. Misadjustment or loose wiring of secondary latch Adjust door and latch switches. switch 2. Defective secondary latch switch 1. Off-alignment of latch switches Adjust door and latch switches. 2. Open or loose connection of high voltage circuit especially magnetron filament circuit Large contact resistance will cause lower magnetron filament voltage and cause magnetron to have lower output and/or be intermittent. 3. Defective high voltage component H.V. Inverter Power Supply (U) Magnetron 4. Open or loose wiring of power relay B (RY-1) 5. Defective primary latch switch Check high voltage component according to component test procedure and replace if it is defective. 6. Defective DPC or power relay B (RY-1) Refer to DPC troubleshooting 1. Open or loose wiring of secondary latch switch 2. Off-alignment of secondary latch switch 3. Defective secondary latch switch 1. Decrease in power source voltage Consult electrician 2. Open or loose wiring of magnetron filament circuit.(intermittent oscillation) 3. Aging change of magnetron 1. Shorted primary latch switch 8. Fan motor turns on and turntable rotates when door is opened. 9. Oven does not operate and return to plugged in mode as soon as start pad is pressed. 10. Loud buzzing noise can be heard. 1. Loose fan and fan motor 11. Turntable motor does not rotate. 1. Open or loose wiring of turntable motor 2. Defective turntable motor 12. Oven stops operation during cooking. 1. Open or loose wiring of primary and secondary latch switch 13. Oven returns to plugged in mode after 10 seconds elapses on the Auto sensor cooking mode. 1. Defective DPC Check tighten screws on escutcheon base bracket, D.P.C. board. 2. Operation of thermal cutout 1. Open or loose wiring of sensor terminal from DPC 2. Open steam sensor 3. Defective DPC Adjust door and latch switches. 23

11.2. Troubleshooting of inverter circuit (U) and magnetron NEW H.V. This oven is programmed with a self diagnostic failure code system which will help for troubleshooting. H97, H98, and H99 are the provided failure codes to indicate magnetron and inverter circuit problem areas. This section explains failure codes of H97, H98, and H99. First, you must program the DPC by pressing Clock, Timer, Start, Power Level. Program unit for operation. H97, H98, H99 appears in display window a short time after start key is pressed and there is no microwave oscillation. Alternate way to troubleshoot oven with AC Ampere meter used H97, H98, H99 appears in display window a short time after start key is pressed and no microwave oscillation with AC Ampere meter used for troubleshooting 24

12 EXPLODED VIEW AND PARTS LIST EXPLODED VIEW 52 41 49 41 41 41 6 8 11 10 41 41 41 2 9 3 29 38 22 50 1 25 41 12 24 14 31 5 27 16 15 4 28 7 39 18 26 21 19 33 40 32 36 17 35 37 20 34 54 25

DOOR ASSEMBLY D1 D4 D5 D2 D6 D3 ESCUTCHEON BASE ASSEMBLY E4 E1 E8 E7 E6 E5 26

WIRING MATERIALS MAGNETRON W1 W2 CAUTION HEAT SINK (HOT/LIVE) VERY HIGH VOLTAGE AND TEMPERATURE W3 PACKING AND ACCESSORIES Cut into two parts when packing P10 P7 Place in oven P1 ROLLER RING ASSY P6 P3 P5 P4 P2 Cut into two parts when packing. 27